Patellar tendinosis or jumper's knee is an extremely common knee disorder with an estimated incidence of between 13% and 20% in athletic populations.14,15,16
Various possible intrinsic aetiologies for this condition have been proposed in athletes, including abnormal patellar tracking,17
limb length discrepancy,14
and reduced flexibility of the quadriceps and hamstring muscle groups.18
While patellar tendinosis is often diagnosed clinically, magnetic resonance imaging and ultrasound are now well established.6,19,20,21,22
The sonographic features of tendinosis are well described in both the patellar tendon and elsewhere.10,20,23,24
We used four sonographic features for diagnosis and ultrasound follow up. These included tendon size, focal alteration in tendon echotexture, interstitial clefts or tears (fibrillar disruption), and neovascularity. The degree of neovascularity identified in patients with patellar tendinosis is affected by the position of the knee during sonographic assessment. In the extended position, neovascularity appears more florid and when tension is applied on the tendon in flexion, some of the neovascularity is abolished. For the purposes of the study and to ensure continuity, the knee was examined in a consistent position, resting on a pillow. This enabled an assessment to be made on follow up sonography of the degree of neovascularity. When the patient returned at four weeks for the second injection, we often observed that the hypoechoic focus in the proximal patellar tendon had become more echogenic. We postulate that this accumulation of echogenic material relates to the formation of immature scar tissue/granulation tissue, though we have no pathological evidence of this. Furthermore, there were changes in the neovascularity following the autologous blood injection. We anticipated that a decrease in tendon neovascularity would be observed; however, this only occurred in nine patients. An equal number of patients showed an increase in vascularity, which we cannot explain. This occurred despite resolution in symptoms and a return to sporting activity.
What is already known on this topic
- Patellar tendinosis is a common problem causing morbidity in sport. It is often refractory to treatment. Autologous blood injection has been reported as showing promise in the treatment of this condition at other sites, for example in medial and lateral epicondylitis.
What this study adds
- This study reports the technique of dry needling and autologous blood injection under sonographic guidance as a therapeutic option for patellar tendinosis.
- Therapeutic intervention led to a significant improvement in VISA score as a measure of clinical outcome.
We assessed the clinical outcome of patients using VISA. This assesses symptomatology, simple function, and the ability to undertake sporting activity, scored out of 100. It has been validated as a clinical method for assessing the severity of a patient's symptoms in patellar tendinosis and has been shown to be a reliable and reproducible index.13
We were able to demonstrated a significant in improvement in symptoms using our technique.
The injection of autologous blood into tendons has been evaluated in studies assessing the in vitro12
and in vivo10,11
effects on tendons. Taylor and co‐workers assessed the effects of autologous blood injection on the strength of rabbit patellar tendons and found a significant increase in injected tendon strength when compared with the contralateral normal side.12
Connell and co‐workers reported clinical and sonographic improvement in patients treated with autologous blood injections for lateral epicondylitis.10
In our study, the patellar tendon underwent barbotage or “dry needling” before autologous blood injection in all cases included in the study. This technique involves the repeated lancing of the area of abnormal tendon. It is done to stimulate an inflammatory response within the tendon. There is focal disruption of the collagen fibres within the area of tendinosis, so the process of dry needling is done to incite internal haemorrhage. It is then hypothesised that the inflammatory response induces the formation of granulation tissue which strengthens the tendon.11
Although our study design does not allow comment on the mechanism of action of this technique, several workers have postulated possible biological mechanisms that may contribute. Anitua and co‐workers investigated the effects of platelet‐rich clots on human tendon cells in culture. They found that autologous preparations rich in growth factors induce cell proliferation and promote synthesis of angiogenic factors during the healing process.25
Furthermore, it has been hypothesized that basic fibroblast growth factor and transforming growth factor β may act as humoral mediators in the induction of the healing cascade.26
We believe that it is essential that this procedure should be done under ultrasound guidance. Fredberg and co‐workers found that the clinical suspicion of tendonitis could be confirmed by ultrasound evaluation in only one third of cases.6
Ultrasound therefore allows confirmation of the diagnosis and provides an imaging baseline under which the response can be assessed. It allows the area of tendon abnormality to be located precisely and interstitial tears to be identified and targeted for blood injection. Frequently, the abnormality can be quite focal and the injectate can be seen permeating the clefts within the tendon substance. In addition, physiotherapy plays a vital role in the ongoing treatment of patients following a period of rest and the series of injections. We used a standardised protocol based on the findings of Purdam et al
Loading of the patellar tendon was achieved by decline eccentric dips, with incrementally increasing load over three to six months, until the subject had returned to sport. All subjects also received quadriceps, hamstring, and calf stretches. The programme was home based, with regular physiotherapy clinic visits to guide the subject's progression.
There are various limitations to our study. We are, in essence, evaluating two therapies simultaneously. Autologous blood injection and dry needling is combined with physiotherapy as part of our treatment protocol. We therefore do not know the relative importance of the autologous blood injection and the dry needling in the therapeutic outcome of the group studied. Previous workers have identified good results with painful eccentric quadriceps training, with significant improvement in clinical outcome.4
However, most of our patients had undergone a course of physiotherapy, and the tendinosis had proved refractory to this initial treatment. Second, although the VISA score provides an objective measure of clinical outcome in patients treated with this technique, we do not have any other objective measurement of tendon healing. The ultrasound findings are descriptive and rather subjective. It would be difficult to justify biopsy of the tendon to provide histological evidence of tendon healing. With this in mind, ultrasound was chosen as the method to monitor the “healing response” and to observe the sonographic appearances of tendons treated by this new technique. Further research is required with a randomised controlled trial of autologous blood injection/physiotherapy versus physiotherapy alone.